CN104294005A

CN104294005A - Smelting method for Ti-containing stainless steel

Info

Publication number: CN104294005A
Application number: CN201310305612.7A
Authority: CN
Inventors: 巫建平; 金雄杰; 黄华平; 申忠容; 金荣朝
Original assignee: Zhangjiagang Pohang Stainless Steel Co Ltd
Current assignee: Zhangjiagang Pohang Stainless Steel Co Ltd
Priority date: 2013-07-19
Filing date: 2013-07-19
Publication date: 2015-01-21
Anticipated expiration: 2033-07-19
Also published as: CN104294005B

Abstract

The invention relates to a smelting method for Ti-containing stainless steel. The method includes ladle treatment on molten steel after AOD refining. The ladle treatment consists of: after AOD refining tapping, pulling out slag from the surface of the molten steel; putting CaO and low-melting-point mould powder into the molten steel; adding an aluminum block, utilizing ladle bottom blowing of argon to conduct powerful stirring, and inputting titanium sponge at the end of stirring, then conducting medium stirring, and carrying out sampling and temperature measurement at the end; inputting alloys and cooling blocks to carry out fine adjustment on the molten steel components and temperature according to components and temperature, and simultaneously conducting bottom blowing stirring; when alloy input is finished, inputting Ca-Si blocks, then reducing the flow of bottom blowing argon, and conducting weak stirring to complete treatment. The method performs twice deep deoxidation on the molten steel, can improve the actual yield of titanium, at the same time reduces the oxygen content of the molten steel, lowers the content of TiO2, CaO.TiO2 and other inclusions in the molten steel, greatly reduces the water port accretion probability in the continuous casting process, reduces the billet grinding amount, improves the metal actual yield, and improves the surface quality in a rolling process.

Description

A kind of containing the stainless melting method of Ti

Technical field

The present invention relates to a kind of containing the stainless melting method of Ti, belong to stainless steel smelting technical field.

Background technology

Type of stainless steel adds Ti effectively can prevent intergranular corrosion, and wherein typical type of stainless steel has 321 stainless steels, and this steel grade is greater than 0.1% containing Ti amount.Under current working condition, AOD can successfully smelt, but when it is produced, maximum difficult point is to form TiO in continuous casting casting cycle ₂the inclusiones such as/TiN, affect productivity and Molten Steel Cleanliness.

Particular problem has: form TiO containing Ti steel at casting cycle ₂/ TiN, causes the unstable of casting cycle, the easy dross of continous casting sprue, and causing the continuous casting later stage to be cast cannot normally carry out; Containing Ti stainless steel casting blank surface difference, slab reconditioning loss is large, because generating various inclusion containing in Ti stainless steel smelting casting cycle, such as: TiN, TiO ₂, MgOAl ₂o ₃, CaOTiO ₂etc. being enriched in casting billet surface, during steel rolling, easily cause board surface defect, as rigidity scar processed, crackle.

The key solved the problem is: reduce plain steel N content, thus reduces TiN Precipitation Temperature, guarantees that few generation TiN is mingled with as far as possible in continuous casting process.In current AOD smelting technology mainly through: adopt full argon to blow, improve AOD and load the C content of molten steel, in reaction between carbon and oxygen process, effectively de-N.AOD tapping molten steel N can control at below 80ppm, molten steel in bakie in continuous casting [N] <130ppm; Further Oxygen Content in Liquid Steel, thus reduce TiO ₂, MgOAl ₂o ₃, CaOTiO ₂deng the problem of oxide inclusion, AOD refining still cannot solve, and oxygen level also needs further reduction.

Summary of the invention

For solving the problems of the technologies described above, the object of the present invention is to provide a kind of containing the stainless melting method of Ti, by carrying out Ladle Treatment to the molten steel after AOD refining, reduce the total oxygen content in molten steel, thus reduce the probability of various oxide inclusion formation, molten steel purity is improved, improves Continuous Casting Level, improve stainless surface quality.

For achieving the above object, the invention provides a kind of containing the stainless melting method of Ti, its Ladle Treatment after being included in AOD refining, molten steel comprised the following steps:

Skim: after AOD refining tapping, pull out the slag of molten steel surface; Can prevent from by skimming returning S from slag, namely avoiding following reaction occurs

Insulating covering agent drops into: the low melting point covering slag (have adiabatic heat-insulation covering and prevent the effect of secondary oxidation of steel dross inclusion adsorption) dropping into CaO and the 1-1.5Kg/ ton steel of 0.5-1Kg/ ton steel in molten steel; Powdered CaO covers molten steel surface, can play insulation effect, and can stop the O in molten steel and air ₂and N ₂contact, prevents the secondary oxidation of molten steel and molten steel from inhaling N; Increase the input of low melting point covering slag, produce Al at input aluminium deoxidation ₂o ₃afterwards, low melting point covering slag can play the effect of absorption inclusion content in melting steel effectively, improves the purity of molten steel;

Deoxidation: add aluminium block, addition is 1.5-2Kg/ ton steel (to guarantee composition Al>0.1wt% in continuous casting sample), utilizes ladle bottom blowing argon gas to carry out strong mixing, and argon flow amount controls as 500-550Nm ³/ min, churning time is 3-5min, guarantees that deoxidation is abundant, simultaneously the temperature of molten steel and uniform composition in ladle, and stir and terminate to drop into titanium sponge (content of Ti is 98%-99%), the addition of titanium sponge is 2.3-3Kg/ ton steel, then with 250-300Nm ³the argon flow amount of/min carries out the middle stirring of 3-6min, guarantees that ferrotianium melts and evenly, terminates rear sampling thermometric; Al is the superpower deoxidant element of one in smelting iron and steel, and deoxidizing capacity is extremely strong, and reaction principle is: 2 [Al]+3 [O] → Al ₂o ₃;

Contents temperature is finely tuned: drop into alloy according to composition and temperature and cooling block is finely tuned composition and temperature, requires that composition and trough casting temperature computation judge ladle refining amount, the maintenance of bottom blowing simultaneously 500-550Nm according to finished product ³the argon flow amount of/Min stirs 2-3min;

Ca-Si process: after alloy and cooling block drop into, drop into Ca-Si block, addition is 1.0-1.5Kg/ ton steel, then reduces the flow of argon bottom-blowing to 30-60Nm ³/ min carries out weak stirring, and weak stirring 12-18min completes process; Deoxidation products Al ₂o ₃fusing point be 2050 DEG C, in solid-state and plasticity-is poor in molten steel, not yielding, in the operation of rolling, easily form surface imperfection on coil of strip surface, also easy water blocking mouthh in casting cycle, by increasing Ca-Si input amount, adopts Calcium treatment to change Al ₂o ₃form, generates 2CaOAl ₂o ₃siO ₂, fusing point is lower, and plasticity-is good, is easy to float; The low melting point covering slag of early investment, can increase the ability of the inclusion that absorption is floated.

In above-mentioned melting method, preferably, by weight percentage, adopt Ca-Si block to contain the Ca of Si, 28-35wt% of 55-65wt%.Surplus in Ca-Si block is impurity, such as Al, C, P etc.

Provided by the present inventionly can comprise following concrete steps containing the stainless melting method of Ti: batching, electric furnace slightly refine, AOD refining, Ladle Treatment, continuous casting casting, its technical process can be as shown in Figure 1.Here involved batching, electric furnace slightly refine, AOD refining, continuous casting casting can adopt conventional mode to carry out.

Provided by the present invention can be suitable for containing the stainless melting method of Ti comprise the stainless steels such as SA321, SF409 containing Ti stainless steel, but to be not limited thereto.

Provided by the present invention is carry out secondary deep deoxidation to molten steel containing Ti stainless steel smelting method, can improve the casting yield of titanium, lower the oxygen level of molten steel simultaneously, make TiO in molten steel ₂, CaOTiO ₂content Deng inclusion is reduced, and greatly reduces nozzle clogging probability in continuous casting casting cycle, and steel blank regrinding amount reduces, and improves metal casting yield, improves the surface quality in the operation of rolling.

Accompanying drawing explanation

The following drawings is only intended to schematically illustrate the present invention and explain, not delimit the scope of the invention.Wherein:

Fig. 1 the invention provides the process flow sheet containing the stainless melting method of Ti;

Fig. 2 is the process flow sheet of Ladle Treatment.

Embodiment

In order to there be understanding clearly to technical characteristic of the present invention, object and beneficial effect, referring now to Figure of description, following detailed description is carried out to technical scheme of the present invention, but can not be interpreted as to of the present invention can the restriction of practical range.

Embodiment

Present embodiments provide a kind of containing the stainless melting method of Ti, should be SA321 stainless steel containing Ti stainless steel, table 1 be the stainless Composition Control requirement of SA321.

Table 1

Composition	C	Si	N	Cr	Ni	Al	Ti	Ti/C+N
									Target	0.033	0.5	≤0.012	17.6	9.2	0.1	0.25	5.3
Lower limit	0.03	0.4	0	17.5	9.1	0	0.2	5
									The upper limit	0.06	0.7	0.035	18.1	9.5	0.15	0.5	12

After AOD refining tapping, among the trimming of molten steel to the scope of table 1.AOD refining tap is 155Ton, and tapping temperature is 1725 DEG C, goes out composition of steel as shown in table 2.

Table 2

Treated state

C

Si

N

Cr

Ni

T-Al

Ti

DE

AOD taps

0.0125

0.59

0.0073

17.6

9.12

0.002

?

Ladle Treatment that molten steel is comprised the following steps after what the present embodiment provided be included in AOD refining containing Ti stainless steel smelting method, its flow process as shown in Figure 2:

1, skim:

The slag of molten steel surface is pulled out, thermometric after AOD refining tapping.

2, insulating covering agent drops into:

CaO powder 100Kg, low melting point covering slag 150Kg is dropped in molten steel.

3, deoxidation:

Add aluminium block (add-on is ton steel 1.8Kg), (flow is 500Nm to argon bottom-blowing ³/ min) carry out the strong mixing of 3min, stir and terminate to drop into ferrotianium (input amount is ton steel 2.6Kg), then with 300Nm ³the argon flow amount of/min carries out the middle stirring of 5min, guarantees that ferrotianium melts and evenly, terminates rear sampling thermometric.

4, contents temperature fine setting:

The composition of the Ladle Treatment 1 provided according to table 3 carries out the fine setting of composition, and drop into Rhometal 444Kg, ferrochrome exothermic 835Kg, bottom blowing simultaneously keeps 500NM ³the argon flow amount of/min stirs 2min, guarantees temperature uniform component.

Table 3

Treated state	C	Si	N	Cr	Ni	T-Al	Ti	DE
									Ladle Treatment 1	0.0153	0.56	0.0092	17.6	9.06	0.149	0.266	10.9

5, Ca-Si process:

After ladle refining, reduce bottom blowing flow after dropping into Ca-Si180Kg, Ca-Si process, weak stirring 12min, weak stirring terminates front 1min sampling analysis, and result is as shown in table 4.

Table 4

Treated state	C	Si	N	Cr	Ni	T-Al	Ti	DE
									Ladle Treatment 2	0.0302	0.62	0.0101	17.7	9.21	0.142	0.251	6.2

According to the qualified departures of analytical results display product of table 4, arrive continuous casting casting, the parameter of continuous casting is as shown in table 5.

Table 5

Treated state	C	Si	N	Cr	Ni	T-Al	Ti	DE
									Continuous casting	0.0305	0.61	0.0109	17.7	9.22	0.136	0.243	5.9

The comparative data that table 6 is the product obtained containing the stainless melting method of Ti and comparative example (not adding aluminium in Ladle Treatment process) that adopt embodiment.

Table 6

As can be seen from the data of table 6, adopt the oxygen level that can reduce containing the stainless melting method of Ti in molten steel of the present invention, improve the casting yield of titanium, reduce the quantity of inclusion, the nozzle clogging probability in continuous casting casting cycle reduces, and improves productivity.

Claims

1. containing the stainless melting method of Ti, its Ladle Treatment after being included in AOD refining, molten steel comprised the following steps:

Skim: after AOD refining tapping, pull out the slag of molten steel surface;

Insulating covering agent drops into: the low melting point covering slag dropping into CaO and the 1-1.5Kg/ ton steel of 0.5-1Kg/ ton steel in molten steel;

Deoxidation: add aluminium block, addition is 1.5-2Kg/ ton steel, utilizes ladle bottom blowing argon gas to carry out strong mixing, and argon flow amount controls as 500-550Nm ³/ min, churning time is 3-5min, and stir and terminate to drop into titanium sponge, titanium sponge addition is 2.3-3Kg/ ton steel, then with 250-300Nm ³the argon flow amount of/min carries out the middle stirring of 3-6min, terminates rear sampling thermometric;

Contents temperature is finely tuned: drop into alloy according to the composition recorded and temperature and finely tune the composition of molten steel and temperature, bottom blowing simultaneously keeps 500-550Nm ³the argon flow amount of/min stirs 2-3min;

Ca-Si process: after alloy and cooling block drop into, drop into Ca-Si block, addition is 1.0-1.5Kg/ ton steel, then reduces the flow of argon bottom-blowing to 30-60Nm ³/ min carries out weak stirring, completes process after weak stirring 12-18min.

2. the step that according to claim 1 containing the stainless melting method of Ti, wherein, the method comprises batching, electric furnace slightly refines, AOD refining, Ladle Treatment, continuous casting are cast.

3. according to claim 1 and 2 containing the stainless melting method of Ti, wherein, the described Ti stainless steel that contains comprises SA321 or SF409.

4. according to claim 1 containing the stainless melting method of Ti, wherein, by weight percentage, described Ca-Si block contains the Ca of Si, 28-35wt% of 55-65wt%.